Problem: Simplify the following expression: $x = \dfrac{10}{7n} - \dfrac{1}{10n}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $7n$ and $10n$ $\lcm(7n, 10n) = 70n$ $ x = \dfrac{10}{10} \cdot \dfrac{10}{7n} - \dfrac{7}{7} \cdot \dfrac{1}{10n} $ $x = \dfrac{100}{70n} - \dfrac{7}{70n}$ $x = \dfrac{100 -7}{70n}$ $x = \dfrac{93}{70n}$